tpm1: reimplement tpm1_continue_selftest() using tpm_buf

Reimplement tpm1_continue_selftest() using tpm_buf structure.
This is the last command using the old tpm_cmd_t structure
and now the structure can be removed.

Cc: Nayna Jain <nayna@linux.vnet.ibm.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>